The Planetary Report

May/June 1994

From Our Member Magazine

While We Weren't Watching: Apollo's Scientific Exploration of the Moon

If you went around and talked to the men who have I been to the Moon, one of the most remarkable stories you would hear is Apollo 15 astronaut Dave Scott's description of the view he had as he stood next to his lunar rover, high on the slopes of a mountain called Hadley Delta. Beyond Hadley Delta's sweeping flank, 90 meters (300 feet) below, lay the bright, undulating volcanic plains of Palus Putredinis, the Marsh of Decay. Everywhere the land was scarred by impact craters, some worn and smooth, others sharp-rimmed and brilliant white. At the horizon, the rounded peaks of the Apennines, one of the Moon's great mountain ranges, cradled the black dome of the lunar sky.

On the airless Moon, the entire scene was rendered in startling clarity. And out in the middle of this pristine, ancient wilderness, Scott could see a tiny speck: his lunar module, Falcon, more than 5 kilometers (3 miles) away. The view was so breathtaking, Scott says, that for a moment it distracted him from the real reason he and Jim Irwin were there: to hunt for geologic treasure.

Aside from the awe-inspiring view, Scott's story conveys the extraordinary heights Apollo reached during its brief lifetime. Just two years earlier, in July 1969, Apollo 11 astronauts Neil Armstrong and Buzz Aldrin had stayed for 31, hours on a bland acre of moonscape after history's first human lunar landing. In their single moonwalk, which lasted about as long as a feature-length film, they never ventured more than 60 meters (200 feet) from their lander. By the fourth lunar landing, Scott and Irwin were living in a lunar valley for three full days. Improved space suits and back- packs allowed them to take three moonwalks, each lasting as much as seven hours. And, most significant, their battery-powered rover gave them the capability to range miles across the surface and visit spectacular features, including a canyon 1.5 kilometers (1 mile) wide called Hadley Rille. In two short years, NASA had greatly extended the reach of human activities on another world, and it had done so in the name of scientific exploration. But it had happened despite some long odds.

The Premise, and the Promise, of Apollo

With Apollo 11, NASA had met John Kennedy's challenge to land a man on the Moon and return him safely to Earth by decade's end. Television commentators and editorial writers proclaimed that 500 years in the future our century would be remembered for those footsteps on the Sea of Tranquility, when human beings left their home planet to explore the universe.

Within the space agency, there were some who considered Apollo 11 an engineering demonstration, and they urged that it was time to move on to new challenges. You wouldn't ask Lindbergh to fly the Atlantic again, they said; why go back to the Moon?

The answer was that Apollo had given the country the ability to explore other worlds. To the geologists who, with almost childlike excitement, began to study the Apollo 11 lunar samples, the Moon was a 4.6-billion-year history book waiting to be read. Future missions could discover clues to the earliest history and even the origin of the Moon and, by implication, of our own world.

At NASA headquarters, Administrator Tom Paine needed no convincing. He believed that there was another message implicit in Kennedy's challenge, beyond its words: that America should become a spacefaring nation. With Apollo 11, the country had achieved that status; it had only to use it. In Paine's mind, Apollo was just the beginning.

The Exploration Unfolds

So it was that in November 1969 Apollo 12's Pete Conrad and Alan Bean touched down on the lava plains of the Ocean of Storms. The samples they collected gave geologists a valuable comparison with Apollo 11's volcanic rocks. Conrad and Bean also deployed a nuclear-powered scientific station designed to measure seismic activity and analyze the Moon's environment. And, most important for future missions, they touched down within walking distance of the robot Surveyor 3 probe, which had landed on the Moon in 1967. With this pinpoint-landing capability, the way was now clear to visit more difficult and more geologically interesting locales.

Pete Conrad with Surveyor 3 during Apollo 12
Pete Conrad with Surveyor 3 during Apollo 12 Apollo 12 astronaut Pete Conrad poses next to the Surveyor 3 spacecraft in November 1969. Surveyor 3 landed 2 years earlier in April 1967. The Apollo 12 lunar module can be seen in the background. NASA

Apollo 13 astronauts Jim Lovell, Jack Swigert and Fred Haise left Earth in April 1970, bound for the Moon's Fra Mauro highlands in what was to have been Apollo's first true science mission. The mission was lost when the command ship was crippled by an explosion 200,000 miles from Earth. Using their lunar lander as a lifeboat, and with a heroic effort by mission controllers, the men barely made it back to Earth.

In February 1971, Apollo 14's Alan Shepard and Ed Mitchell picked up the torch from Lovell and Haise, exploring Fra Mauro in two moonwalks totaling more than nine hours. They found a landscape much rougher than the lava plains visited by previous moonwalkers; instead it was like an airless, rock-strewn Sahara, with undulating ridges that reminded the men of sand dunes. This roughness was probably due to the presence of material ejected from the giant Imbrium impact basin, 550 kilometers (340 miles) to the north. Finding the date of Imbrium's formation-one of the most significant events in lunar evolution-was Apollo 14's main geologic objective.

But that turned out to be more difficult than Shepard and Mitchell had anticipated. Like their predecessors, they found it difficult to navigate on a surface devoid of trees and other familiar landmarks, without even the atmospheric haze that serves on Earth as a visual cue of distance.

On their second excursion, Shepard and Mitchell struggled to find the rim of the 335-meter-diameter (1,100-foot) Cone crater, where the samples of Imbrium ejecta were most likely to be found. Tired, and cutting into their reserves of oxygen and cooling water, the men were called back just short of their goal-which lay, unbeknownst to them, only 20 meters (65 feet) away. Nevertheless, the Apollo 14 samples gave geologists a shaky but usable date for Imbrium's origin: 3.85 billion years.

Prior to Apollo 11, one researcher had stated that if so much as a single gram of lunar material was brought to Earth the scientific understanding of the Moon would increase a millionfold. Now, after three Apollo landings and one robotic sample return mission by the Soviets (Luna 16), there were 98 kilograms (216 pounds) of lunar rocks and soil in NASA's Lunar Receiving Laboratory and in laboratories around the world.

Spurred by the presence of lunar rocks on Earth, researchers had developed extraordinary techniques for analyzing the samples, using only tiny amounts of material at a time, able to detect individual atoms within a sample. Seismic data from the Apollo 12 and 14 scientific stations were allowing geophysicists to probe the Moon's interior. And for astronomers, lunar dust was teeming with subatomic particles emitted by the Sun, and tracked with the trails of high-energy cosmic rays.

An Interrupted Quest

But even as Apollo's explorations were bearing fruit, they were curtailed. In January 1970, faced with the leanest budget in nine years, NASA canceled the final lunar mission, Apollo 20, and assigned its Saturn V booster to the Skylab Earth-orbit space station. The following summer, two more missions—Apollo 18 and 19—fell under the budgetary ax. And Tom Paine's vision for the post-Apollo era—which included space stations in Earth orbit and in lunar orbit, a base on the Moon, and human missions to Mars—had been rejected by the Nixon administration; only plans for a reusable space shuttle survived.

Ironically, the cancellations came just as NASA was planning its most ambitious lunar explorations. Apollo 15 was the first of the extended lunar expeditions, called J-missions, that finally began to realize Apollo's scientific potential. Apollo 15's climactic moment came on August 1, 1971, as Scott and Irwin, prospecting on the slopes of Hadley Delta, found a small white chunk of rock, of a type called anorthosite, that proved to be a piece of the Moon's primordial crust.

Astronaut Dave Scott in the Lunar Receiving Lab
Astronaut Dave Scott in the Lunar Receiving Lab Dave Scott visits the Genesis Rock in the Lunar Receiving Laboratory on Earth. This piece of anorthosite is one of the oldest rocks ever studied by scientists, who dated it at about 4.4 billion years old. Scott and Jim Irwin collected it on the flank of Hadley Delta mountain during the Apollo 15 mission. NASA

For the astronauts, who had spent months training with geologists for their lunar fieldwork, it was a moment of triumph. For the scientists themselves, this find—which reporters nicknamed the Genesis Rock—confirmed that the Moon had once been covered by an ocean of liquid rock, or magma, which later solidified. The magma ocean concept was to become a key element in scientists' scenarios for the early evolution of Earth and the other terrestrial planets. Meanwhile, in lunar orbit aboard Apollo 15's command module, Al Worden surveyed the Moon with a battery of high-powered cameras and sensors, amassing a haul of data that almost eclipsed the discoveries by his two crewmates on the surface.

A Last Hurrah, and a Distracted Nation

The final lunar landings bettered even Apollo 15's extraordinary success. On Apollo 16, in April 1972, John Young and Charlie Duke became the first astronauts to explore the Moon's ancient central highlands. Expecting to discover evidence of volcanic activity, they found instead a landscape shaped by almost unimaginable violence: the meteorite and asteroid impacts that battered the Moon during its infancy and youth.

Finally, in December, Apollo 17 saw Gene Cernan and geologist-astronaut Jack Schmitt, the first scientist to walk on another world, exploring a canyon at the rim of the Serenitatis basin. There they found rocks that dated almost all the way back to the formation of the Moon, 4.6 billion years ago, along with tiny beads of orange, red and black glass that had been ejected from deep in the lunar interior by spectacular eruptions called fire fountains.

Thanks to a remotely controlled camera on the rover, Cernan and Schmitt's activities were broadcast to Earth live, in color and with remarkable clarity. Apollo 17 was nothing less than a space spectacular: It epitomized the boldness, ingenuity and above all the extraordinary human impact of the first visits to another world.

But by that time, most of us had stopped watching. Even before Apollo 11, the nation's attention had been divided. Concerned over the war in Vietnam, the endangered environment and the deteriorating inner cities, we no longer paid much attention to yet another team of astronauts exploring the Moon. By the time of Apollo 17, television networks had stopped covering the moonwalks in their entirety. The scientists working on the lunar samples had long accepted the Moon program's premature end. And at NASA, planners were already looking ahead to the space shuttle. Few mourned Apollo.

A Challenge More Than Met

Today, across the span of 25 years, it is difficult to comprehend how quickly we accomplished the first human explorations of the Moon—or how readily we gave them up. No one who participated in Apollo—least of all the astronauts themselves—thought it had accomplished all it was capable of. But even in its short life, Apollo gave us our money's worth. The Apollo lunar samples, totaling 381 kilograms (838 pounds), along with thousands of photographs and other data, are still yielding clues to the world that has been our Rosetta stone for deciphering planetary evolution.

In retrospect, Apollo stands out as a bright spot in a troubled era in our history, perhaps the last great act this country will ever perform out of a sense of optimism. What we did on that July night in 1969—and five more times in the 41 short months that followed-is still worth remembering: we touched the face of another world, and became a people without limits.

The Planetary Report • May/June

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